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100
80
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0
0
−50
−100
−150 −200
∆
ƒ(Hz)
−250
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−350
Figure 10.6
QCM-D correlation plot of dissipation difference,
Δ
D
, as a function of
frequency shift,
f
, for the adsorption of small (
) and large (
) cubosomes on hydro-
philic silica. The solid line represents the adsorption and fusion of vesicles on silica
surface. Schematic drawings illustrate the intact crystalline nanoparticles after adsorp-
tion (left) and lipid bilayer formed from vesicle fusion (right). [Reprinted with permis-
sion from Vandoolaeghe et al. (2009b). Copyright 2009 by the American Chemical
Society.]
Δ
curve suggests that the interfacial layer is built up by slow attachment of
nanoparticles rather than their molecular components. This conclusion is rea-
sonable as random lateral organization of bound nanoparticles is visible from
fl uorescence microscopy, and QCM-D demonstrates the large change in dis-
sipation and the high stability of the viscoelastic particle at the interface
(Vandoolaeghe et al., 2009b).
Different adsorption processes for the LCNP compared to the lamellar
vesicles on hydrophilic Si interfaces were revealed by QCM-D (Vandoolaeghe
et al., 2009b). The lamellar vesicles adsorb intact on hydrophilic surfaces at
low coverage and transform into a bilayer arrangement after a critical cover-
age (Reimhult et al., 2002, 2003). The collapse of the surface-attached vesicles
is shown as a kink in the correlation plot of dissipation change,
Δ
D
, as a func-
tion of frequency shift,
f
, as seen with the solid line in Figure 10.6. The drop
in dissipation signifi es the disruption and spreading of the vesicle and release
of solvent mass. For the adsorption of LCNP, a monotonic increase of
Δ
Δ
D
versus
f
with no kink shows that the bound particles remain largely intact
with signifi cant amount of acoustically coupled water. The schematic drawings
in Figure 10.6 illustrate the different adsorption behavior of nonlamellar crys-
talline particles and lamellar vesicles on the hydrophilic Si surface.
Δ
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